#include "parser.hpp"
#include <cstdlib>
#include "std.hpp"

#ifdef DEMO
static const int TEXTLIMIT = 16384;
#else
static const int TEXTLIMIT = 1024 * 1024 - 1;
#endif

enum { STMTS_PROG, STMTS_BLOCK, STMTS_LINE };

static bool isTerm(int c)
{
	return c == ':' || c == '\n';
}

Parser::Parser(Toker& t) : toker(&t), main_toker(&t) {}

ProgNode* Parser::parse(const string& main)
{
	incfile = main;

	consts             = new DeclSeqNode();
	structs            = new DeclSeqNode();
	funcs              = new DeclSeqNode();
	datas              = new DeclSeqNode();
	StmtSeqNode* stmts = 0;

	try {
		stmts = parseStmtSeq(STMTS_PROG);
		if (toker->curr() != EOF)
			exp("end-of-file");
	} catch (Ex) {
		delete stmts;
		delete datas;
		delete funcs;
		delete structs;
		delete consts;
		throw;
	}

	return new ProgNode(consts, structs, funcs, datas, stmts);
}

void Parser::ex(const string& s)
{
	throw Ex(s, toker->pos(), incfile);
}

void Parser::exp(const string& s)
{
	switch (toker->curr()) {
	case NEXT:
		ex("'Next' without 'For'");
	case WEND:
		ex("'Wend' without 'While'");
	case ELSE:
	case ELSEIF:
		ex("'Else' without 'If'");
	case ENDIF:
		ex("'Endif' without 'If'");
	case ENDFUNCTION:
		ex("'End Function' without 'Function'");
	case UNTIL:
		ex("'Until' without 'Repeat'");
	case FOREVER:
		ex("'Forever' without 'Repeat'");
	case CASE:
		ex("'Case' without 'Select'");
	case ENDSELECT:
		ex("'End Select' without 'Select'");
	}
	ex("Expecting " + s);
}

string Parser::parseIdent()
{
	if (toker->curr() != IDENT)
		exp("identifier");
	string t = toker->text();
	toker->next();
	return t;
}

void Parser::parseChar(int c)
{
	if (toker->curr() != c)
		exp(string("'") + char(c) + string("'"));
	toker->next();
}

StmtSeqNode* Parser::parseStmtSeq(int scope)
{
	a_ptr<StmtSeqNode> stmts(new StmtSeqNode(incfile));
	parseStmtSeq(stmts, scope);
	return stmts.release();
}

void Parser::parseStmtSeq(StmtSeqNode* stmts, int scope)
{
	for (;;) {
		while (toker->curr() == ':' || (scope != STMTS_LINE && toker->curr() == '\n'))
			toker->next();
		StmtNode* result = 0;

		int pos = toker->pos();

#ifdef DEMO
		if (Toker::chars_toked > TEXTLIMIT) {
			ex("Demo version source limit exceeded");
		}
#endif
		switch (toker->curr()) {
		case INCLUDE: {
			if (toker->next() != STRINGCONST)
				exp("include filename");
			string inc = toker->text();
			toker->next();
			inc = inc.substr(1, inc.size() - 2);

			//WIN32 KLUDGE//
			char buff[MAX_PATH], *p;
			if (GetFullPathName(inc.c_str(), MAX_PATH, buff, &p))
				inc = buff;
			inc = tolower(inc);

			if (included.find(inc) != included.end())
				break;

			ifstream i_stream(inc.c_str());
			if (!i_stream.good())
				ex("Unable to open include file");

			Toker i_toker(i_stream);

			string t_inc   = incfile;
			incfile        = inc;
			Toker* t_toker = toker;
			toker          = &i_toker;

			included.insert(incfile);

			a_ptr<StmtSeqNode> ss(parseStmtSeq(scope));
			if (toker->curr() != EOF)
				exp("end-of-file");

			result = new IncludeNode(incfile, ss.release());

			toker   = t_toker;
			incfile = t_inc;
		} break;
		case IDENT: {
			string ident = toker->text();
			toker->next();
			string tag = parseTypeTag();
			if (arrayDecls.find(ident) == arrayDecls.end() && toker->curr() != '=' && toker->curr() != '\\'
				&& toker->curr() != '[') {
				//must be a function
				ExprSeqNode* exprs;
				if (toker->curr() == '(') {
					//ugly lookahead for optional '()' around statement params
					int nest = 1, k;
					for (k = 1;; ++k) {
						int c = toker->lookAhead(k);
						if (isTerm(c))
							ex("Mismatched brackets");
						else if (c == '(')
							++nest;
						else if (c == ')' && !--nest)
							break;
					}
					if (isTerm(toker->lookAhead(++k))) {
						toker->next();
						exprs = parseExprSeq();
						if (toker->curr() != ')')
							exp("')'");
						toker->next();
					} else
						exprs = parseExprSeq();
				} else
					exprs = parseExprSeq();
				CallNode* call = new CallNode(ident, tag, exprs);
				result         = new ExprStmtNode(call);
			} else {
				//must be a var
				a_ptr<VarNode> var(parseVar(ident, tag));
				if (toker->curr() != '=')
					exp("variable assignment");
				toker->next();
				ExprNode* expr = parseExpr(false);
				result         = new AssNode(var.release(), expr);
			}
		} break;
		case IF: {
			toker->next();
			result = parseIf();
			if (toker->curr() == ENDIF)
				toker->next();
		} break;
		case WHILE: {
			toker->next();
			a_ptr<ExprNode>    expr(parseExpr(false));
			a_ptr<StmtSeqNode> stmts(parseStmtSeq(STMTS_BLOCK));
			int                pos = toker->pos();
			if (toker->curr() != WEND)
				exp("'Wend'");
			toker->next();
			result = new WhileNode(expr.release(), stmts.release(), pos);
		} break;
		case REPEAT: {
			toker->next();
			ExprNode*          expr = 0;
			a_ptr<StmtSeqNode> stmts(parseStmtSeq(STMTS_BLOCK));
			int                curr = toker->curr();
			int                pos  = toker->pos();
			if (curr != UNTIL && curr != FOREVER)
				exp("'Until' or 'Forever'");
			toker->next();
			if (curr == UNTIL)
				expr = parseExpr(false);
			result = new RepeatNode(stmts.release(), expr, pos);
		} break;
		case SELECT: {
			toker->next();
			ExprNode*         expr = parseExpr(false);
			a_ptr<SelectNode> selNode(new SelectNode(expr));
			for (;;) {
				while (isTerm(toker->curr()))
					toker->next();
				if (toker->curr() == CASE) {
					toker->next();
					a_ptr<ExprSeqNode> exprs(parseExprSeq());
					if (!exprs->size())
						exp("expression sequence");
					a_ptr<StmtSeqNode> stmts(parseStmtSeq(STMTS_BLOCK));
					selNode->push_back(new CaseNode(exprs.release(), stmts.release()));
					continue;
				} else if (toker->curr() == DEFAULT) {
					toker->next();
					a_ptr<StmtSeqNode> stmts(parseStmtSeq(STMTS_BLOCK));
					if (toker->curr() != ENDSELECT)
						exp("'End Select'");
					selNode->defStmts = stmts.release();
					break;
				} else if (toker->curr() == ENDSELECT) {
					break;
				}
				exp("'Case', 'Default' or 'End Select'");
			}
			toker->next();
			result = selNode.release();
		} break;
		case FOR: {
			a_ptr<VarNode>     var;
			a_ptr<StmtSeqNode> stmts;
			toker->next();
			var = parseVar();
			if (toker->curr() != '=')
				exp("variable assignment");
			if (toker->next() == EACH) {
				toker->next();
				string ident = parseIdent();
				stmts        = parseStmtSeq(STMTS_BLOCK);
				int pos      = toker->pos();
				if (toker->curr() != NEXT)
					exp("'Next'");
				toker->next();
				result = new ForEachNode(var.release(), ident, stmts.release(), pos);
			} else {
				a_ptr<ExprNode> from, to, step;
				from = parseExpr(false);
				if (toker->curr() != TO)
					exp("'TO'");
				toker->next();
				to = parseExpr(false);
				//step...
				if (toker->curr() == STEP) {
					toker->next();
					step = parseExpr(false);
				} else
					step = new IntConstNode(1);
				stmts   = parseStmtSeq(STMTS_BLOCK);
				int pos = toker->pos();
				if (toker->curr() != NEXT)
					exp("'Next'");
				toker->next();
				result = new ForNode(var.release(), from.release(), to.release(), step.release(), stmts.release(), pos);
			}
		} break;
		case EXIT: {
			toker->next();
			result = new ExitNode();
		} break;
		case GOTO: {
			toker->next();
			string t = parseIdent();
			result   = new GotoNode(t);
		} break;
		case GOSUB: {
			toker->next();
			string t = parseIdent();
			result   = new GosubNode(t);
		} break;
		case RETURN: {
			toker->next();
			result = new ReturnNode(parseExpr(true));
		} break;
		case BBDELETE: {
			if (toker->next() == EACH) {
				toker->next();
				string t = parseIdent();
				result   = new DeleteEachNode(t);
			} else {
				ExprNode* expr = parseExpr(false);
				result         = new DeleteNode(expr);
			}
		} break;
		case INSERT: {
			toker->next();
			a_ptr<ExprNode> expr1(parseExpr(false));
			if (toker->curr() != BEFORE && toker->curr() != AFTER)
				exp("'Before' or 'After'");
			bool before = toker->curr() == BEFORE;
			toker->next();
			a_ptr<ExprNode> expr2(parseExpr(false));
			result = new InsertNode(expr1.release(), expr2.release(), before);
		} break;
		case READ:
			do {
				toker->next();
				VarNode*  var  = parseVar();
				StmtNode* stmt = new ReadNode(var);
				stmt->pos      = pos;
				pos            = toker->pos();
				stmts->push_back(stmt);
			} while (toker->curr() == ',');
			break;
		case RESTORE:
			if (toker->next() == IDENT) {
				result = new RestoreNode(toker->text());
				toker->next();
			} else
				result = new RestoreNode("");
			break;
		case DATA:
			if (scope != STMTS_PROG)
				ex("'Data' can only appear in main program");
			do {
				toker->next();
				ExprNode* expr = parseExpr(false);
				datas->push_back(new DataDeclNode(expr));
			} while (toker->curr() == ',');
			break;
		case TYPE:
			if (scope != STMTS_PROG)
				ex("'Type' can only appear in main program");
			toker->next();
			structs->push_back(parseStructDecl());
			break;
		case BBCONST:
			if (scope != STMTS_PROG)
				ex("'Const' can only appear in main program");
			do {
				toker->next();
				consts->push_back(parseVarDecl(DECL_GLOBAL, true));
			} while (toker->curr() == ',');
			break;
		case FUNCTION:
			if (scope != STMTS_PROG)
				ex("'Function' can only appear in main program");
			toker->next();
			funcs->push_back(parseFuncDecl());
			break;
		case DIM:
			do {
				toker->next();
				StmtNode* stmt = parseArrayDecl();
				stmt->pos      = pos;
				pos            = toker->pos();
				stmts->push_back(stmt);
			} while (toker->curr() == ',');
			break;
		case LOCAL:
			do {
				toker->next();
				DeclNode* d    = parseVarDecl(DECL_LOCAL, false);
				StmtNode* stmt = new DeclStmtNode(d);
				stmt->pos      = pos;
				pos            = toker->pos();
				stmts->push_back(stmt);
			} while (toker->curr() == ',');
			break;
		case GLOBAL:
			if (scope != STMTS_PROG)
				ex("'Global' can only appear in main program");
			do {
				toker->next();
				DeclNode* d    = parseVarDecl(DECL_GLOBAL, false);
				StmtNode* stmt = new DeclStmtNode(d);
				stmt->pos      = pos;
				pos            = toker->pos();
				stmts->push_back(stmt);
			} while (toker->curr() == ',');
			break;
		case '.': {
			toker->next();
			string t = parseIdent();
			result   = new LabelNode(t, datas->size());
		} break;
		default:
			return;
		}

		if (result) {
			result->pos = pos;
			stmts->push_back(result);
		}
	}
}

string Parser::parseTypeTag()
{
	switch (toker->curr()) {
	case '%':
		toker->next();
		return "%";
	case '#':
		toker->next();
		return "#";
	case '$':
		toker->next();
		return "$";
	case '.':
		toker->next();
		return parseIdent();
	}
	return "";
}

VarNode* Parser::parseVar()
{
	string ident = parseIdent();
	string tag   = parseTypeTag();
	return parseVar(ident, tag);
}

VarNode* Parser::parseVar(const string& ident, const string& tag)
{
	a_ptr<VarNode> var;
	if (toker->curr() == '(') {
		toker->next();
		a_ptr<ExprSeqNode> exprs(parseExprSeq());
		if (toker->curr() != ')')
			exp("')'");
		toker->next();
		var = new ArrayVarNode(ident, tag, exprs.release());
	} else
		var = new IdentVarNode(ident, tag);

	for (;;) {
		if (toker->curr() == '\\') {
			toker->next();
			string    ident = parseIdent();
			string    tag   = parseTypeTag();
			ExprNode* expr  = new VarExprNode(var.release());
			var             = new FieldVarNode(expr, ident, tag);
		} else if (toker->curr() == '[') {
			toker->next();
			a_ptr<ExprSeqNode> exprs(parseExprSeq());
			if (exprs->exprs.size() != 1 || toker->curr() != ']')
				exp("']'");
			toker->next();
			ExprNode* expr = new VarExprNode(var.release());
			var            = new VectorVarNode(expr, exprs.release());
		} else {
			break;
		}
	}
	return var.release();
}

DeclNode* Parser::parseVarDecl(int kind, bool constant)
{
	int       pos   = toker->pos();
	string    ident = parseIdent();
	string    tag   = parseTypeTag();
	DeclNode* d;
	if (toker->curr() == '[') {
		if (constant)
			ex("Blitz arrays may not be constant");
		toker->next();
		a_ptr<ExprSeqNode> exprs(parseExprSeq());
		if (exprs->size() != 1 || toker->curr() != ']')
			exp("']'");
		toker->next();
		d = new VectorDeclNode(ident, tag, exprs.release(), kind);
	} else {
		ExprNode* expr = 0;
		if (toker->curr() == '=') {
			toker->next();
			expr = parseExpr(false);
		} else if (constant)
			ex("Constants must be initialized");
		d = new VarDeclNode(ident, tag, kind, constant, expr);
	}
	d->pos  = pos;
	d->file = incfile;
	return d;
}

DimNode* Parser::parseArrayDecl()
{
	int    pos   = toker->pos();
	string ident = parseIdent();
	string tag   = parseTypeTag();
	if (toker->curr() != '(')
		exp("'('");
	toker->next();
	a_ptr<ExprSeqNode> exprs(parseExprSeq());
	if (toker->curr() != ')')
		exp("')'");
	if (!exprs->size())
		ex("can't have a 0 dimensional array");
	toker->next();
	DimNode* d        = new DimNode(ident, tag, exprs.release());
	arrayDecls[ident] = d;
	d->pos            = pos;
	return d;
}

DeclNode* Parser::parseFuncDecl()
{
	int    pos   = toker->pos();
	string ident = parseIdent();
	string tag   = parseTypeTag();
	if (toker->curr() != '(')
		exp("'('");
	a_ptr<DeclSeqNode> params(new DeclSeqNode());
	if (toker->next() != ')') {
		for (;;) {
			params->push_back(parseVarDecl(DECL_PARAM, false));
			if (toker->curr() != ',')
				break;
			toker->next();
		}
		if (toker->curr() != ')')
			exp("')'");
	}
	toker->next();
	a_ptr<StmtSeqNode> stmts(parseStmtSeq(STMTS_BLOCK));
	if (toker->curr() != ENDFUNCTION)
		exp("'End Function'");
	StmtNode* ret = new ReturnNode(0);
	ret->pos      = toker->pos();
	stmts->push_back(ret);
	toker->next();
	DeclNode* d = new FuncDeclNode(ident, tag, params.release(), stmts.release());
	d->pos      = pos;
	d->file     = incfile;
	return d;
}

DeclNode* Parser::parseStructDecl()
{
	int    pos   = toker->pos();
	string ident = parseIdent();
	while (toker->curr() == '\n')
		toker->next();
	a_ptr<DeclSeqNode> fields(new DeclSeqNode());
	while (toker->curr() == FIELD) {
		do {
			toker->next();
			fields->push_back(parseVarDecl(DECL_FIELD, false));
		} while (toker->curr() == ',');
		while (toker->curr() == '\n')
			toker->next();
	}
	if (toker->curr() != ENDTYPE)
		exp("'Field' or 'End Type'");
	toker->next();
	DeclNode* d = new StructDeclNode(ident, fields.release());
	d->pos      = pos;
	d->file     = incfile;
	return d;
}

IfNode* Parser::parseIf()
{
	a_ptr<ExprNode>    expr;
	a_ptr<StmtSeqNode> stmts, elseOpt;

	expr = parseExpr(false);
	if (toker->curr() == THEN)
		toker->next();

	bool blkif = isTerm(toker->curr());
	stmts      = parseStmtSeq(blkif ? STMTS_BLOCK : STMTS_LINE);

	if (toker->curr() == ELSEIF) {
		int pos = toker->pos();
		toker->next();
		IfNode* ifnode = parseIf();
		ifnode->pos    = pos;
		elseOpt        = new StmtSeqNode(incfile);
		elseOpt->push_back(ifnode);
	} else if (toker->curr() == ELSE) {
		toker->next();
		elseOpt = parseStmtSeq(blkif ? STMTS_BLOCK : STMTS_LINE);
	}
	if (blkif) {
		if (toker->curr() != ENDIF)
			exp("'EndIf'");
	} else if (toker->curr() != '\n')
		exp("end-of-line");

	return new IfNode(expr.release(), stmts.release(), elseOpt.release());
}

ExprSeqNode* Parser::parseExprSeq()
{
	a_ptr<ExprSeqNode> exprs(new ExprSeqNode());
	bool               opt = true;
	while (ExprNode* e = parseExpr(opt)) {
		exprs->push_back(e);
		if (toker->curr() != ',')
			break;
		toker->next();
		opt = false;
	}
	return exprs.release();
}

ExprNode* Parser::parseExpr(bool opt)
{
	if (toker->curr() == NOT) {
		toker->next();
		ExprNode* expr = parseExpr1(false);
		return new RelExprNode('=', expr, new IntConstNode(0));
	}
	return parseExpr1(opt);
}

ExprNode* Parser::parseExpr1(bool opt)
{
	a_ptr<ExprNode> lhs(parseExpr2(opt));
	if (!lhs)
		return 0;
	for (;;) {
		int c = toker->curr();
		if (c != AND && c != OR && c != XOR)
			return lhs.release();
		toker->next();
		ExprNode* rhs = parseExpr2(false);
		lhs           = new BinExprNode(c, lhs.release(), rhs);
	}
}

ExprNode* Parser::parseExpr2(bool opt)
{
	a_ptr<ExprNode> lhs(parseExpr3(opt));
	if (!lhs)
		return 0;
	for (;;) {
		int c = toker->curr();
		if (c != '<' && c != '>' && c != '=' && c != LE && c != GE && c != NE)
			return lhs.release();
		toker->next();
		ExprNode* rhs = parseExpr3(false);
		lhs           = new RelExprNode(c, lhs.release(), rhs);
	}
}

ExprNode* Parser::parseExpr3(bool opt)
{
	a_ptr<ExprNode> lhs(parseExpr4(opt));
	if (!lhs)
		return 0;
	for (;;) {
		int c = toker->curr();
		if (c != '+' && c != '-')
			return lhs.release();
		toker->next();
		ExprNode* rhs = parseExpr4(false);
		lhs           = new ArithExprNode(c, lhs.release(), rhs);
	}
}

ExprNode* Parser::parseExpr4(bool opt)
{
	a_ptr<ExprNode> lhs(parseExpr5(opt));
	if (!lhs)
		return 0;
	for (;;) {
		int c = toker->curr();
		if (c != SHL && c != SHR && c != SAR)
			return lhs.release();
		toker->next();
		ExprNode* rhs = parseExpr5(false);
		lhs           = new BinExprNode(c, lhs.release(), rhs);
	}
}

ExprNode* Parser::parseExpr5(bool opt)
{
	a_ptr<ExprNode> lhs(parseExpr6(opt));
	if (!lhs)
		return 0;
	for (;;) {
		int c = toker->curr();
		if (c != '*' && c != '/' && c != MOD)
			return lhs.release();
		toker->next();
		ExprNode* rhs = parseExpr6(false);
		lhs           = new ArithExprNode(c, lhs.release(), rhs);
	}
}

ExprNode* Parser::parseExpr6(bool opt)
{
	a_ptr<ExprNode> lhs(parseUniExpr(opt));
	if (!lhs)
		return 0;
	for (;;) {
		int c = toker->curr();
		if (c != '^')
			return lhs.release();
		toker->next();
		ExprNode* rhs = parseUniExpr(false);
		lhs           = new ArithExprNode(c, lhs.release(), rhs);
	}
}

ExprNode* Parser::parseUniExpr(bool opt)
{
	ExprNode* result = 0;
	string    t;

	int c = toker->curr();
	switch (c) {
	case BBINT:
		if (toker->next() == '%')
			toker->next();
		result = parseUniExpr(false);
		result = new CastNode(result, Type::int_type);
		break;
	case BBFLOAT:
		if (toker->next() == '#')
			toker->next();
		result = parseUniExpr(false);
		result = new CastNode(result, Type::float_type);
		break;
	case BBSTR:
		if (toker->next() == '$')
			toker->next();
		result = parseUniExpr(false);
		result = new CastNode(result, Type::string_type);
		break;
	case OBJECT:
		if (toker->next() == '.')
			toker->next();
		t      = parseIdent();
		result = parseUniExpr(false);
		result = new ObjectCastNode(result, t);
		break;
	case BBHANDLE:
		toker->next();
		result = parseUniExpr(false);
		result = new ObjectHandleNode(result);
		break;
	case BEFORE:
		toker->next();
		result = parseUniExpr(false);
		result = new BeforeNode(result);
		break;
	case AFTER:
		toker->next();
		result = parseUniExpr(false);
		result = new AfterNode(result);
		break;
	case '+':
	case '-':
	case '~':
	case ABS:
	case SGN:
		toker->next();
		result = parseUniExpr(false);
		if (c == '~') {
			result = new BinExprNode(XOR, result, new IntConstNode(-1));
		} else {
			result = new UniExprNode(c, result);
		}
		break;
	default:
		result = parsePrimary(opt);
	}
	return result;
}

ExprNode* Parser::parsePrimary(bool opt)
{
	a_ptr<ExprNode> expr;
	string          t, ident, tag;
	ExprNode*       result = 0;
	int             n, k;

	switch (toker->curr()) {
	case '(':
		toker->next();
		expr = parseExpr(false);
		if (toker->curr() != ')')
			exp("')'");
		toker->next();
		result = expr.release();
		break;
	case BBNEW:
		toker->next();
		t      = parseIdent();
		result = new NewNode(t);
		break;
	case FIRST:
		toker->next();
		t      = parseIdent();
		result = new FirstNode(t);
		break;
	case LAST:
		toker->next();
		t      = parseIdent();
		result = new LastNode(t);
		break;
	case BBNULL:
		result = new NullNode();
		toker->next();
		break;
	case INTCONST:
		result = new IntConstNode(atoi(toker->text()));
		toker->next();
		break;
	case FLOATCONST:
		result = new FloatConstNode(atof(toker->text()));
		toker->next();
		break;
	case STRINGCONST:
		t      = toker->text();
		result = new StringConstNode(t.substr(1, t.size() - 2));
		toker->next();
		break;
	case BINCONST:
		n = 0;
		t = toker->text();
		for (k = 1; k < t.size(); ++k)
			n = (n << 1) | (t[k] == '1');
		result = new IntConstNode(n);
		toker->next();
		break;
	case HEXCONST:
		n = 0;
		t = toker->text();
		for (k = 1; k < t.size(); ++k)
			n = (n << 4) | (isdigit(t[k]) ? t[k] & 0xf : (t[k] & 7) + 9);
		result = new IntConstNode(n);
		toker->next();
		break;
	case PI:
		result = new FloatConstNode(3.1415926535897932384626433832795f);
		toker->next();
		break;
	case BBTRUE:
		result = new IntConstNode(1);
		toker->next();
		break;
	case BBFALSE:
		result = new IntConstNode(0);
		toker->next();
		break;
	case IDENT:
		ident = toker->text();
		toker->next();
		tag = parseTypeTag();
		if (toker->curr() == '(' && arrayDecls.find(ident) == arrayDecls.end()) {
			//must be a func
			toker->next();
			a_ptr<ExprSeqNode> exprs(parseExprSeq());
			if (toker->curr() != ')')
				exp("')'");
			toker->next();
			result = new CallNode(ident, tag, exprs.release());
		} else {
			//must be a var
			VarNode* var = parseVar(ident, tag);
			result       = new VarExprNode(var);
		}
		break;
	default:
		if (!opt)
			exp("expression");
	}
	return result;
}